1. Field of the Invention
The present invention relates to a head suspension of a hard disk drive incorporated in an information processor such as a personal computer.
2. Description of the Related Art
A head suspension of a hard disk drive includes a load beam, a head supported with the load beam, and a slider attached to the head. The head suspension has a shock property that determines a lift-off of the slider from the surface of a hard disk when a shock is applied. The shock property of the head suspension is dependent on the weight of the load beam.
For example, a first head suspension has a load beam having a thickness (t) of 51 μm, a length (lL) of 7 mm, and a gram load of 2.5 gf that is applied by the load beam to a head, and a second head suspension has a load beam having a thickness (t) of 30 μm, a length (lL) of 5.5 mm, and a gram load of 2.5 gf. If a shock of 1 msec duration (1 msec in half wavelength) is applied to these head suspensions, a slider of the first head suspension lifts at an acceleration of 628 G and a slider of the second head suspension lifts at an acceleration of 1103 G.
FIG. 13 and FIG. 14 show a relationship between lift-off G of a head suspension and lift-off G of a hard disk drive, in which FIG. 13 is a graph showing the result of a 2.5-inch hard disk drive and in which FIG. 14 is a graph showing the result of a 1-inch hard disk drive.
The shock property of the head suspension is expressed with the magnitude of a shock at which a slider of the load beam of the head suspension is lifted from the surface. The shock property of the head suspension is referred to as “lift-off G” indicative of the magnitude of the shock that causes a lift-off of the slider. The “lift-off G” is also indicative of the shock property of the hard disk drive.
In the 2.5-inch hard disk drive of FIG. 13, shock input including two kinds of waveforms, one having a half wavelength with 1 msec duration and the other having a half wavelength with 0.4 msec duration is applied. In the 1-inch hard disk drive of FIG. 14, shock input including three kinds of waveforms, one having a half wavelength with 2 msec duration, another having a half wavelength with 1 msec duration, and the remaining having a half wavelength with 0.4 msec duration is applied.
In the 2.5-inch hard disk drive of FIG. 13, even if the lift-off G of the head suspension is increased, the lift-off G of the hard disk drive does not increase so much. In the 1 msec duration, a slope thereof is y≈0, and in the 0.4 msec duration, a slope thereof is y=0.27.
On the other hand, in the 1-inch hard disk drive with a small size of FIG. 14, when the lift-off G of the head suspension is increased, the lift-off G of the hard disc drive increases evenly. In the 2 msec duration, a slope thereof is y=0.90, in the 1 msec duration, a slope thereof is y=0.85, and in the 0.4 msec duration, a slope thereof is y=0.81.
FIG. 15 and FIG. 16 is respectively a graph showing a change of generated acceleration to shock input at a front end of an arm to which a head suspension attached according to a time change. An abscissa indicates time and an ordinate indicates acceleration. The data shown in FIG. 15 relates a 2.5-inch hard disk drive and the data shown in FIG. 16 relates to a 1-inch hard disk drive. In FIGS. 15 and 16, magnitude of shock input is set to have 0.4 msec duration and 200 G.
As is apparent from FIG. 15 and FIG. 16, the 2.5-inch hard disk drive generated an arm action larger than that in the 1-inch hard disk drive. Therefore, in the 2.5-inch hard disk drive, the shock property of the hard disk drive is largely dependent on not only the weight of the head suspension but also the arm action. In contrast, in the 1-inch hard disk drive, the shock property of the hard disk drive is hardly dependent on the arm action and it is mainly dependent on the weight of the head suspension.
Thereby, in a miniaturized hard disk drive such as a 1-inch hard disk drive, it has been found that the shock property of the hard disk drive can be improved by only increasing the lift-off G of the head suspension.
Accordingly, to improve the shock property of a head suspension in the miniaturized hard disk drive, thinning a load beam of the head suspension to reduce weight is effective.
FIG. 17 is a perspective view showing a head suspension 101 according to a related art. The head suspension 101 has a base plate 103, a load beam 105 integrated with the base plate 103, and a flexure 107 supported to the load beam 105. The load beam 105 includes a rigid part or beam 109 and a resilient part or hinge 111.
FIG. 18 is a partly sectioned view showing an example of a hard disk drive in which the head suspensions 101 of FIG. 17 are arranged. As shown in FIG. 18, for example, the base plate 103 of the head suspension 101 is attached to an arm 115 of a carriage 113 by swaging.
The carriage 113 is turned around a spindle 119 by a positioning motor 117 such as a voice coil motor. A head 121 of the head suspension 101 is moved to a target track on a disk 123 according to pivoting of the carriage 113 around the spindle 119.
When the disk 123 rotates at high speed, the head 121 slightly floats from the disk 123 against gram load.
In such a head suspension 101 including the load beam 105 integrated with the resilient part, the load beam 105 with a length lL is made thin as countermeasure considering such a weight as described above.
However, the load beam 105 made thin in order to improve the shock property, the resilient part 111 becomes thin together with the load beam. This causes higher stress acting on the resilient part 111, so that it is impossible to increase a spring load for determining the gram load as the load applied onto the head 121 to a certain value or more.
On the other hand, there is a head suspension including a rigid part and a resilient part separated from and fixed to the rigid part. According to the head suspension, the resilient part is made thinner than the rigid part in order to set the resilient part to a low spring constant and secure rigidity of the rigid part. When the load beam is made thin entirely in order to improve the shock property while keeping the relationship between the thicknesses of the rigid part and resilient part, the resilient part is also made thin. It is impossible to increase a spring load to a certain value or more like the above case.
To solve the problem, expanding a width of a base end side of the load beam 105, namely, a width of the resilient part 111 is effective.
FIG. 19 is a plan view showing a hard disk drive 125 in which the head suspension 101 of FIG. 17 is incorporated.
As shown in FIG. 19, the head suspension 101 is installed in the hard disk drive 125 for example. The hard disk drive 125 has the arms 115, a wire 127, disks 123, and the like. When a width B of the base end side of the load beam is expanded, the width of the arm 115 to which the head suspension 101 is attached is also expanded. This results in overlapping of the arm 115 with the disk 123 or interference thereof with the wire 127 in plan view of FIG. 19. Overlapping the arm 115 with the disk 123 involves a risk that the arm 115 and the disk 123 come in contact with each other due to shock input. Therefore, the overlapping of the arm 115 with the disk 123 and interference of the arm 115 with the wire 127 must be avoided.
Even if the width B of the base end side of the load beam 105 is expanded such that the arm 115 of the head suspension 101 does not overlap with the disk 123 or it does not interfere with the wire 127, it prevent the hard disk drive 125 from miniaturizing. The related art mentioned above is disclosed in Japanese Unexamined Patent Application Publication H09-282624.